Project Summary Infants born very preterm are at increased risk of experiencing adverse developmental outcomes in childhood, resulting in substantial burdens for those infants and their families. Recent research in the field of behavioral epigenomics has indicated that preterm birth may have long term impacts on epigenetic regulation and that differential DNA methylation is linked to variability in cognitive and behavioral function. However, there is a lack of longitudinal epigenomic data in the published literature and thus it is unclear if preterm-associated epigenomic variations are persistent in childhood, or if epigenomic differences in early life are predictive of later developmental outcomes. DNA methylation can also be used to estimate epigenetic age acceleration which has received increasing attention as a potential risk factor for degenerative diseases in adults. However, there is some evidence that epigenetic aging may be related to positive developmental characteristics in childhood. With funds from our prior award (R01 HD084515-01A1), we studied the relationships between early life medical complications and neurobehavior with DNA methylation and epigenetic age, identifying numerous notable relationships in our cohort of very preterm infants (NOVI). However, these studies were cross-sectional in nature and should be followed up with repeated measure of epigenomic data. The NOVI cohort was also selected for inclusion in the NIH Environmental Influences on Child Health Outcomes (ECHO) consortium (UG3 OD23347) and selected to proceed to the next phase of the award (UH3 OD23347) which provides funding to support extensive phenotypic characterization of our children through age 7, including numerous neurodevelopmental assessments. Thus, we are proposing a competitive renewal to build on our prior work and leverage the extensive and high-quality outcome data being obtained through ECHO. We propose a longitudinal study of DNA methylation and epigenetic aging in a rigorously phenotyped cohort of infants that were born very preterm (< 30 weeks gestation). We aim to study how neonatal medical complications and neurobehavioral responses influence trajectories of DNA methylation and epigenetic aging in childhood, and whether these trajectories track with neurodevelopmental trajectories or are informative for later impairments. We also aim to develop an algorithm that incorporates childhood epigenomic factors with other known risk factors to improve the precision of predictions about which infants are at highest risk of developmental impairments. The successful completion of our study will provide novel and rich data demonstrating the early life experiences among very preterm infants that influence patterns of DNA methylation and epigenetic aging in childhood, characterize how those epigenetic factors are linked to later developmental outcomes, and provide a predictive tool to identify children that are at greatest risk later developmental impairment.